Interesting question, thank you.
The whole functionality of Ranorex is implemented in the RanorecCore C library.

RanorexPython is only a Python wrapper, the same functions as in RanorexCore, I planed to write an object oriented wrapper in Python, but I have no time.

RanorexNet is a .NET wrapper assembly, in .NET you cannot have functions, I made an object oriented wrapper with classes, properties and members like in .NET framework.

It would be interesting to write a Ruby wrapper the same way as the RanorexNet wrapper, with objects.
See: http://www.rubycentral.com/book/ext_ruby.html -> Wrapping C structures
So I'm sorry, you cannot use Ranorex directly from Ruby at the moment, you must write a wrapper.
I would like to write such a wrapper, Ruby is a very interesting language, but I haven't the time at the moment.

It would really be a great feature for Ranorex to support Ruby because of the exceptional testing frameworks that are available for it like RSpec (http://rspec.info/) and Shoulda. I would love to be able to drive a gui test using Rspec the way a Selenium test can be driven from it.

We are currently developing on several new test automation interfaces. We are also informed about the popularity of ruby especially in test communities and keep an eye on changes. Nevertheless, we can't ensure that Ranorex will support Ruby as a test automation language.